Shop Built Foam Cutter

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Project by Dragonsrite posted 10-11-2012 07:05 PM 3265 views 14 times favorited 11 comments Add to Favorites Watch

This is a hot-wire foam cutter I created last summer when I had a need to cut odd shaped pieces of styrofoam insulation. The stretcher assembly is made from pallet stringers and the base is just plywood and some pine that was laying about the shop. This project also has my first mortise & tenon joint (pic 3).

The guitar string wire is made “hot” using a 0-30V Lambda current-limiting power supply (pic 4) which I use for electrolysis too – which is why it is not hard-wired to the cutter.

As you can see in the last picture, the cut quality is very good. It sure beats any other method of cutting foam that I have tried. Easier, generally faster and a LOT less mess (none at all).

As always, any comments, good, bad or indifferent are welcome.

Thanks for looking.

-- Dragonsrite, Minnesota

11 comments so far

View mloy365's profile


444 posts in 3272 days

#1 posted 10-11-2012 07:44 PM

I need to cut a mess of styrofoam sometime soon. What is the heat source? Oh, BTW, this is a great idea! Very nice idea.

-- Mike - Northern Upper Michigan

View Dragonsrite's profile


136 posts in 3539 days

#2 posted 10-11-2012 08:07 PM

The source of heat is the current flowing through the wire which causes the wire to get hot – guitar string in this case. If you look real close in the first picture under the eye-bolt you will see the wire. Currently I’m using a steel ‘B’ string for acoustic guitars. The high ‘E’ string broke due to too much current or cutting pressure or tension from the cutter (or any / all of the fore-mentioned).

The ideal wire to use is nichrome which is made to get hot when a current is passed through it; like in a toaster.

-- Dragonsrite, Minnesota

View Bagtown's profile


1739 posts in 3872 days

#3 posted 10-11-2012 10:24 PM

Way fancier than mine.
I use a high E string but my current is probably less as I just hook up my 12V battery charger.
I needed to cut pieces of insulation for knock outs in a concrete countertop.
What do you need to cut the foam for?

-- Mike - In Fort McMurray Alberta

View Dragonsrite's profile


136 posts in 3539 days

#4 posted 10-12-2012 01:12 AM

One of my long-term projects is a mini-garage for the grandkids power wheels jeep. My wife thought it would be a wonderful idea to make the attic into a winter house for the outdoor cats. The roof on this structure is of the gambrel style (think barn roof) so there are some interesting shaped voids that I needed to fill with styrofoam insulation. The foam cutter worked perfectly to make those pieces.

Once my brother found out about the cutter, he requested my assistance in cutting some 4” styrofoam to insulate a small space under their steps. Lots of odd angles and interesting shapes there too.

When I was looking around the internet to see how people were cutting styrofoam, I noticed that most of them were using a 12V battery charger. I just happened to have the Lambda power source hanging around. I find that I only look at the current when I set up for cutting foam. I run between 2-4 amps with the ‘B’ string (2 for 1” thick & 4 for the 4”). The 1.5” pink insulation in picture 5 was cut with 2.5 amps.

I know; too much information :-)

Thank you for looking and commenting.

-- Dragonsrite, Minnesota

View lightweightladylefty's profile


3256 posts in 3854 days

#5 posted 10-12-2012 03:58 AM

It certainly is nice to be able to make your own tools. Even though I rarely cut styrofoam, I’ve always thought it would be nice to have one since using one in high school art class a long, long time ago. I now cut styrofoam on the bandsaw but it sure is messy.


-- Jesus is the ONLY reason for ANY season.

View bobasaurus's profile


3531 posts in 3326 days

#6 posted 10-12-2012 03:30 PM

Looks really nice. Check out a similar one I built for work:
Your overhead arm piece is prettier than mine and has fancier joinery… mine’s just lag-bolted but joints.

-- Allen, Colorado (Instagram @bobasaurus_woodworking)

View Grumpymike's profile


2310 posts in 2457 days

#7 posted 10-12-2012 03:58 PM

model train shops and hobby stores get big bucks for smaller versions of these.
B or E string and a battery charger … you guys are great. Thanks for the tip and the post

-- Grumpy old guy, and lookin' good Doin' it. ... Surprise Az.

View Dragonsrite's profile


136 posts in 3539 days

#8 posted 10-12-2012 04:03 PM

I’ve only used my cutter three times now – well, 3 sessions. It usually sits up on a high shelf out of the way. I never even thought of the bandsaw. After trying various knives, a hacksaw blade and a hand saw I had to find something that wouldn’t make such a mess.

I think yours is a bit more heavy duty. I like the spring tensioner. What kind of wire did you use? I also like the variac, but I don’t think that electrically isolates the wire from the line voltage.

As for the “prettier” & “fancier joinery”; wellll…. that’s just a symptom of woodworking fever. I don’t even think of simple butt joints or the like now days. Besides I had to try M&T sometime, right?

GrumpyGrandpa here. That’s what the grandkids call me anyway.

I saw some of those big buck units that are for sale. It’s hard to justify the price for such a simple device. I’m glad this post has given you some ideas. Be sure to check out the link that Bobasaurus provided. Some good ideas in his version.

-- Dragonsrite, Minnesota

View Mainiac Matt 's profile

Mainiac Matt

8409 posts in 2470 days

#9 posted 10-12-2012 06:51 PM

Keep your work area very well ventilated… the fumes are nasty stuff!

-- I yam what I yam and that's all what I yam

View Dragonsrite's profile


136 posts in 3539 days

#10 posted 10-12-2012 07:58 PM

I agree SSNVet. Thank you for the tip.

-- Dragonsrite, Minnesota

View Brad_Nailor's profile


2539 posts in 4099 days

#11 posted 10-13-2012 10:50 PM

Yes I was just going to add that..You might want to set up a small fan just to lightly blow some air away from you while you use it..the fumes are very toxic..
Very nice version of one of these..I used to do model train layouts and I always wanted one of these..the cleanest way to shape foam..


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